Carbon nanostructures such as linear carbon nanotubes and sheet-like graphene are known to date in which carbon atoms are arranged in parallel at intervals on the order of nanometers. Such carbon nanostructures are obtained by, for example, a method including supplying a source gas containing carbon while heating a fine catalyst such as iron to thereby grow carbon nanostructures from the catalyst (refer to, for example, Japanese Unexamined Patent Application Publication No. 2005-330175).
In the above existing manufacturing method, during the growth of carbon nanofilaments constituting the carbon nanostructures, it is difficult to control a growth direction from the catalyst, and kinks of the grown carbon nanofilaments easily occur. The occurrence of such kinks generates structural defects such as a five-membered ring and a seven-membered ring in the carbon nanofilaments, resulting in a local increase in the resistance or the like. In addition, it becomes difficult to bundle a plurality of carbon nanofilaments at a high density.
In view of the above, a method has been proposed in which a catalyst is oxidized, and the oxidized catalyst is divided while being subjected to carburizing heat treatment to thereby grow carbon nanofilaments between the resulting divided surfaces (refer to Japanese Unexamined Patent Application Publication No. 2013-237572).